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Thread: Rev Limiter

  1. #1
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    Rev Limiter

    OK i have a 5 speed trans in my SC, and i found this on a web page saying my car has a built in rev limiter is this true, and could you adjust this? I'm not sure but 6200 rpm's might tear my motor .


    A rev limiter is designed to keep you from over revving your engine. All SCís
    and XR7ís with the 3.8L supercharged engine redline at 5000 rpm. Those cars
    equipped with the manual transmission do not rev limit until 6200 rpm though.
    The 4R70W equipped cars rev limit at approximately 5500 rpm. This means
    that in both applications, you would be able to rev your car higher than the
    designed red line. But once you hit the rev limiter the EEC will cut spark to the
    engine so that your rpms do not go any higher.

  2. #2
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    past redline, you run the risk of collapsing your hydraulic lifters and beating your pushrods to a pulp.... ask me how i know this...

  3. #3
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    Quote Originally Posted by sinhumane View Post
    past redline, you run the risk of collapsing your hydraulic lifters and beating your pushrods to a pulp.... ask me how i know this...
    How do you know this? hehe I've always thought about this too, with better rockers and maybe with aftermarket pushrods/lifters can you reach the limit safely?

  4. #4
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    not sure about readjusting the rev limiter, but you cal buy and install one from jegs or summit.

  5. #5
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    what kind would work with the stock DIS system , and thanks for the info fellas .

  6. #6
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    Well it a relatively simple circuit with a Cap (as a filter) and a relay (tuning this is where the knowledge/experience would be needed), and use the AC singal generated by either the Cam or Crank sensors.

  7. #7
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    It's a fuel cut.

    EDIS has two wires to the ECU...

    SAW --> EDIS = Pulsewidth based timing command.
    PIP --> ECU = Pulsewidth based feedback on how much timing is being used.

    There isn't a "OMG!CutSpark!" wire.

    Even if you cut the SAW cable, EDIS will still spark at base timing of 10*.

  8. #8
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    Out of curiosity, why would you not consider going with a chip that can adjust all the different limiters that are in the ECU?

    Fraser

  9. #9
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    Quote Originally Posted by fturner View Post
    Out of curiosity, why would you not consider going with a chip that can adjust all the different limiters that are in the ECU?

    Fraser
    Uhh....

    In his own post, he said that he has a 5-speed.... And he said that he can already rev to 6200, far beyond where he needs to rev.....

    Why would he want to adjust his rev limiter??

  10. #10
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    He's the one that asked, everyone answered with an aftermarket system, and I suggested a chip instead.....

    Fraser

  11. #11
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    Yeah... Didn't I just say that the factory computer's stratey for limiting RPMs is to cut fuel???

    Something about fuel delivery cutting off at 6000rpms under high load doesn't sit will with me... I wonder why

    I'll give you credit that a chip would give him more flexibility than the aftermarket options, yet the issue is still trying to fix the driver with a computer....

  12. #12
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    I plan on getting a chip after all my mod's are done. my main worry right now is over revving, and i really don't want to damage my engine . the engine in my SC seems to be in really good shape. i used a stethoscope to listen to all the internals, and to me ever things working as it should.

  13. #13
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    I know a tach with a shift light would help, but i really don't want that on my dash. because i like the lay out of the inside from the factory , the only mod i plan on doing inside the car would be a triple gauge pod . what I'm looking for is a plug n play rev limiter that will plug right into the stock dis system , and lower the rev limit until my mods are all done .

  14. #14
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    Quote Originally Posted by Silenced View Post
    Yeah... Didn't I just say that the factory computer's stratey for limiting RPMs is to cut fuel???

    Something about fuel delivery cutting off at 6000rpms under high load doesn't sit will with me... I wonder why

    I'll give you credit that a chip would give him more flexibility than the aftermarket options, yet the issue is still trying to fix the driver with a computer....
    There is actually several limiters involving both fuel and spark, and they come in to play in several stages.... all ranging from fuel enrichment and spark pull initially, to shutting off half the injectors to complete fuel shutoff. All of these can be adjusted to when they come into play. Things like Load, ECT, ACT, MPH, RPM and calculations done to determine what gear the transmission is in all determine which stage is used.

    Now thats something, you actually gave me credit for knowing something .

    Fraser

  15. #15
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    Hehe I never said you didn't know about EEC

    An ignition timing drop, and throwing more fuel at it when it gets to 5500 would be a good start, and would probably help slow the climb down.

    The ultimate solution though is to LIFT YOUR DAMN FOOT! I'm sure you're new to driving a 5-speed, but just practice.... Go out and beat the crap out of your car pretending 4000rpms is where you "NEED" to shift, so that you get the hang of it. If you overshoot 4000ish when you're practicing, who cares, right?

    I'd be more worried about hitting the actual fuel cut and spiking lean than collapsing a hydraulic lifter like Tyler's piece did.

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